It is not a trivial matter to locate users and their movements with fine granularity from mobile activity alone. Most positioning systems use GPS with A-GPS support (or a similar satellite system) to actively monitor the location of the device. However for a mobile operator it is not really an option to actively monitor every user for several reasons:                In almost all cases GPS data is only available in the user's mobile device which the operator simply has no access to;        Forcefully pushing down an application to the users mobile device can be a hard privacy bargain to sell;        Even if users agree, developing and maintaining applications for all mobile types is costly;        Not to mention that constant active positioning is battery-draining and leads to worse user experience.        
Some prior art in this field is as follows:
Identification via Location-Profiling in GSM Networks (2008) Yoni De Mulder, George Danezis, Lejla Batina, Bart Preneel
In this paper, the authors used simple first-order markov chains and hierarchical clustering to profile the users' movement from GSM location data. They claim 80% accuracy for user identification from these profiles in a subsequent period and that information gathered in one month is so rich that it can be used to identify users for a long time after.
An online PDF version is available at: www0.cs.ucl.ac.uk/staff/G.Danezis/papers/GSMLocation-profile.pdf
Mobility Profiler: A Framework for Discovering Mobile User Profiles (2008) Ali Murat, Demirbas Murat, Eagle Nathan
This paper introduces a complete mobility profiler framework also handling problems such as celltower oscillations (i.e. ping-pongs). They construct cell mobility paths and reduce ping-pongs by identifying repeatedly oscillating cell pairs and convert them to cell clusters. Afterwards, they used sequential a priori algorithm to filter out and evaluate dominant patterns. These patterns will build up the mobility profile of that user.
Online PDF version: www.cse.buffalo.edu/tech-reports/2008-17.pdf